Abstract

Landing for many species, such as the queen concho Strombus gigas, have been reduced markedly in recent years, and adequate information on stock status needed for management is not available. A fishery-independent survey of the queen conch resource was conducted off the west and east coasts of Puerto Rico. Areas were stratified into presumed "conch" and "non-conch" strata based on fishermen information in an attempt to Ibwer the 95% confidence limits of the estimates of abundance and maximize sampling effort. Transects were conducted at each station, with data coIlected by divers using visual census. Data were coIlected on conch abundance, length. age, on habitat type, and depth distribution. Gn the west coast. average density within the conch stratum was 9.2 conchs/ha; in the non-conch density was 3.89 conchs/ha. Average density over aIl stations was 8.49 conchs/ha. The estimated population abundance over aIl stations and in the west conch stratum were 755.884 and 608.580, respectively. On the east coast, average densities were 7.28 conchs/ha in the conch stratum and 6.68 conchs/ha in the non-conch stratum. Average density over aIl stations was 7.49 conchs/ha. The over aIl estimate of abundance was 722.272. Estimations of variance (confidence limits) were calculated using bootstrap methods. Results showed that overaIl abundance confidence limits (95%) for the west coast were 580,000 to 1.8 million and for the east coast were 487.000 to 1.2 million individuals. Most of the conch found were juveniles. Juvenile density was highest on seagrass for both survey areas. Adult density was highest on algal plain and sea grass. Data were post-stratified into high and low density habitats based on results from the west coast conch stratum. Significant preferences were found for habitat strata for juveniles and adults in the west coast but no preferences were found on the east coast when the habitats were pooled in high and low yield areas. Abundance of juveniles decIined rapidly with depth. Abundance of adults was highest in the in the 61 - 80 ft (19 - 25 m) and 51 - 70 ft (16 - 22 m) depth zones for the west and east coasts, respectively.

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